• Title/Summary/Keyword: 이온확산

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A study on the lattice defects in $LiNbO_3$ single crystal by crystal by $OH^-$ absorption band ($OH^-$ 흡수밴드에 의한 $LiNbO_3$ 단결정의 격자결함에 관한 연구)

  • 조용석;강길영;윤종규
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.8 no.3
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    • pp.401-406
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    • 1998
  • For the applications in optical waveguides and devices, LiNbO_3$ single crystals need to overcome the weakness of optical damage due to the inhomogeneities of laser-induced refractive index. This problem can be solved by doping of Mg in LiNbO_3$ and proton exchange of LiNbO_3$. In this study, to understand the mechanism of optical damage resistance in LiNbO_3$, the changes of lattice defects in LiNbO_3$ caused by MgO doping and acid treatment were observed indirectly by $OH^-$ absorption bands using a FT-IR spectrophotometer. The effect of lattice defects on temperature, heat-treatment and polishing were also investigated. It is shown that MgO doping increases optical damage resistance by generating the defects of $Mg_{Nb}^{2+}$ in the lattice of LiNbO_3$, and that proton exchange by implantation of $H^+$ ion in the hexagonally closest packed oxygen layers on the surface of LiNbO_3$, makes lattice defects, which diffuse into the crystal after heat-treatment above $400^{\circ}C$.

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Durability of Alkali-Activated Blast Furnace Slag Concrete: Chloride Ions Diffusion (알칼리 활성 슬래그 콘크리트의 내구성: 콘크리트의 염소이온 확산)

  • Nam, Hong Ki;Kyu, Park Jae;San, Jung Kyu;Hun, Han Sang;Hyun, Kim Jae
    • Journal of the Korean Society of Safety
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    • v.30 no.4
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    • pp.120-127
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    • 2015
  • The aim of the present study is to investigate some characteristics of concrete according to addition of blast furnace slag and alkali-activator dosages. Blast furnace slag was used at 30%, 50% replacement by weight of cement, and liquid sulfur having NaOH additives was chosen as the alkaline activator. In order to evaluate characteristics of blast furnace slag concrete with sulfur alkali activators, compressive strength test, total porosity, chloride ions diffusion coefficient test were performed. The early-compressive strength characteristics of blast furnace slag concrete using a sulufr-alkali activators was compared with those of reference concrete and added 30, 50% blast furnace slag concrete. Also, Blast furnace slag concrete using sulfur-alkali activators enhanced the total porosity, chloride ions diffusion coefficient than two standard concrete. Alkali-activated blast furnace slag concrete was related to total porosity, compressive strength and chloride ions diffusion coefficient each others. As a result, it should be noted that the sulfur-alkali activators can not only solve the demerit of blast furnace slag concrete but also offer the chloride resistance of blast furnace slag concrete using sulfur alkali activators to normal concrete.

Evaluation of Durability Characteristics of High Performance Shotcrete Using Fly Ash (폐석탄회를 이용한 고성능 숏크리트의 내구특성 평가)

  • Park, Cheol-Woo;Lee, Hyeon-Gi;Kang, Tae-Sung
    • Journal of the Korea Concrete Institute
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    • v.22 no.3
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    • pp.305-311
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    • 2010
  • The industrial by-product market has increased at a geometric rate worldwide with the rapid economic growth. At present time, conventional disposal methods of industrial by-products in Korea including landfill, incineration and storage already have reached their limits. In this study, the industrial by-products such as fly ash and silicafume were used as mineral admixtures, which are commonly added to concrete mix to inhance the economic efficiency, long-term strength and durability of concrete, to determine the optimized mix proportion of high performance shotcrete. Through the series of tests (compressive strength test, accelerated chloride ion penetration test, measurement of chloride diffusion coefficient). The results of the study showed that the proposed mix proportions satisfied the requirements of domestic as well as international guidelines for shotcrete, with a higher durability than the existing shotcrete.

The Change in Geotechnical Properties of the Deposited Clay Contaminated by Leachate from Waste Disposals (침출수로 오염된 퇴적점토의 역학적 특성변화)

  • Ha, Kwang-Hyun;Lee, Sang-Eun
    • Journal of the Korean GEO-environmental Society
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    • v.7 no.3
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    • pp.43-54
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    • 2006
  • In this paper, the uniaxial, triaxial compression tests and consolidation tests on the clay sample substituted initial pore water for pollutant were performed to evaluate the change in geotechnical properties of the contaminated clay. The contaminant transport analysis on embankment type landfill using the MT3D model was also performed to evaluate the extent of transport and diffusion. There was tendency that strength, compressibility and permeability has increased with the increase in the concentration of NaCl solution. The increase in the strength and compressibility of sample saturated with leachate was higher than samples saturated with NaCl solution, but in the permeability coefficient was lower. As the result of contaminant transport analysis, the predicted concentration was in high with the increase in the initial concentration of $Cl^-$ ion and increased in a non-linear form. The transportation distance calculated with use of regression equation between the distance from contaminant source and the concentration of $Cl^-$ ion was increased with the increase in the initial concentration.

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Fabrication of Sb-doped $SnO_2$ transparent conducting films by sol-gel dip coating and their characteristics (솔-젤 Dip Coating에 의한 Sb-doped $SnO_2$ 투명전도막의 제조 및 특성)

  • 임태영;오근호
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.13 no.5
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    • pp.241-246
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    • 2003
  • The transparent conducting thin film of ATO (antimony-doped tin oxide) was successfully fabricated on$SiO_2$/glass substrate by a sol-gel dip coating method. The crystalline phase of the ATO thin film was identified as SnO$_2$ major phase and the film thickness was about 100 nm/layer at the withdrawal speed of 50 mm/minute. Optical transmittance and electrical resistivity of the 400 nm-thick ATO thin film which was annealed under nitrogen atmosphere were 84% and $5.0\times 10^{-3}\Omega \textrm{cm}$, respectively. It was found that the $SiO_2$ layer inhibited Na ion diffusion and the formation of impurities like $Na_2SnO_3$ or SnO while increasing Sb ion concentration and higher ratio of $Sb^{5+}/Sb^{3+}$in the film. Annealing at nitrogen atmosphere leads to the reduction of $Sn^{4+}$ as well as $Sb^{5+}$ resulting in decrease of the electrical resistivity of the film.

A Study on the Estimation of Corrosion Protection Performance of Concrete Containing Ground Granulated Blast-Furnace Slag for Massive Coastal Structures (매시브한 해양구조물 적용을 위한 고로슬래그 혼입 콘크리트의 방청성능 평가에 관한 연구)

  • Yoo, Jae-Kang;Kim, Dong-Suk;Park, Sang-Joon;Won, Chul;Lee, Sang-Soo
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2002.11a
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    • pp.87-91
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    • 2002
  • This paper investigates the corrosion inhibition and the reduction of hydration heat properties of Ground Granulated Blast-Furnace Slag (GGBFS) added concrete. Since the massive civil structure is vulnerable to the thermal crack by hydration. adiabatic temperature rising tests were performed for water-binder ratios from 43.2% to 47.3%, while replacing 15% to 50% of cement with GGBFS of equal weight. Then, the corrosion protection performance was evaluated using cylindrical specimens embedded with steel reinforcement according to the combination of 3 W/B ratios and 2 levels of chloride ion quantity. The corrosion area of the embedded steel ban was determined using the high pressure steam curing method specified in KS F 2561. The test results showed that the replacement of GGBFS was effective in reducing the hydration heat. The corrosion area of the embedded steel ban decreased as the replacement of GGBFS increased. However, the corrosion area of the steel bar was proportional to the autoclave cycle and the chloride ion quantity. Among the tested specimens, compressive strength, reduction of hydration heat, and corrosion inhibition performance were excellent when 50% of cement was replaced with GGBFS of equal weight.

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Visualization of Natural Convection Heat Transfer on Horizontal Cylinder Using the Copper Electroplating System (전기도금계를 이용한 수평관 외부 자연대류의 시각화)

  • Heo, Jeong-Hwan;Chung, Bum-Jin
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.35 no.1
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    • pp.43-51
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    • 2011
  • Natural convection heat transfer phenomena on a horizontal cylinder have been studied experimentally in order to investigate the applicability of analogy experimental methodology using a copper electroplating system and to visualize the local heat transfer rates depending on the angular position and the diameter of the horizontal cylinder. In the copper electroplating system, the copper ion produced at the anode moves by convection and diffusion to the cathode and reduces at the cathode, representing the heat transfer. By using aluminum cathode with a distinguishable color, the amount of copper plated could visualize the amount of heat transferred depending on the angular position of the cylinder. The diameter of the cylinder is varied from 0.01m to 0.15m, which correspond to Rayleigh numbers in the range of $1.73{\times}10^7$ to $5.69{\times}10^{11}$. The test results are in good agreement with existing heat transfer correlations.

The latest movement of PVD coating for industrial application (산업용 PVD코팅 기술 최근 동향)

  • Im, Sang-Won
    • Proceedings of the Korean Institute of Surface Engineering Conference
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    • 2016.11a
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    • pp.33-55
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    • 2016
  • PVD(Physical Vapour Deposition)코팅은 70년대 미국의 Multi-arc이란 기업에 의해 질화물계나 탄화물계 피막 증착이 가능한 아크이온플레팅(Arc Ion Plating) 기술이 산업에 소개되어, 주로 내마모나 내구성을 요구하는 금형, 절삭공구, 산업용 부품 분야 등에 적용되면서 꾸준한 성장세를 거듭해 왔다. 최근 들어 PVD기술은 그 수요의 급증과 더불어 보다 진화된 형태의 코팅장치 및 코팅피막들이 산업에 소개 되고 있다. 먼저 절삭가공분야에는 new composition, nano composite, multi-element composition, multi-layer, SML(Self Modification Layer)등의 코팅피막들이 단독 또는 조합된 형태로 개발되어 철계 소재를 대상으로 고경도 소재의 고속가공, 저경도~중경도 소재의 중속~고속 광범위영역에서 동시 절삭을 가능케 하였고, 비철.비금속 소재 절삭용으로 종전의 가스방식의 DLC(a-C:H)코팅을 훨씬 능가하는 ta-C Plus(Ultra super DLC) 코팅이 개발되어 고 Si함량의 Al-Si계 합금, Cu-W계, 고 섬유 CFRP, CFRM 및 반소결 상태의 세라믹 소재들을 황삭에서 정삭까지 단일 공정으로 절삭이 가능한 고성능 공구들이 개발보급되고 있다. 금속 성형분야에는 고장력 강판을 냉간에서 성형 가능한 Lubricative multi-layer coating, 열간 또는 고온에서 성형이 가능한 functional multi layer과 이형성이 더한층 개선된 dimpled(or embossed) functional multi layer 코팅들이 개발되어 산업현장에 빠르게 확산되고 있다. PVD 코팅의 또 다른 주요 적용분야로 의료분야를 들 수 있는데, 이는 코팅의 대다수가 고경도의 생체친화적인 특성을 가진데 착안되었으며, 흔히 현대성 질환이라 일컫는 과민성 체질, 과체중 및 허약체질 환자의 증가와 각종 재해 및 사고의 증가 및 인간 수명 증가에 따른 인공적인 시술의 요구증가에 편승하여 이 분야의 시장 또한 가파르게 성장하고 있다. 또한 대량으로 양산 적용단계에 접어든 자동차 핵심부품들을 비롯해서 각종 산업용, 방산용 기계 부품에도 성능 향상, 내구성 향상, 환경친화성 등 다양한 목적으로 확대 적용되고 있는 사례들을 본 발표를 통해 간략하게나마 소개하고자 한다.

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Characterization of Selectively Absorbing Properties of Indium Tin Oxide Thin Films by UV-VIS-IR Spectroscopy (UV-VIS-IR 분광법에 의한 산화 인듐 주석 박막의 선택적 투과 흡수 특성 관찰)

  • Lee, Jeon-Kook;Lee, Dong-Heon;Cho, Nam-Hee
    • Analytical Science and Technology
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    • v.5 no.1
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    • pp.135-142
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    • 1992
  • Indium tin oxide(ITO) films coated on the window glass selectively transmit the solar energy and infrared. We call this system passive solar collectors. Selectively absorbing properties of sol gel dip coated ITO films were characterized by UV-VIS-NIR spectroscopy. The effects of heat treating temperature, time, atmosphere, substrate and barrier layers are concerned. Indium tin oxide films heat-treated at $500^{\circ}C$ in a reducing atmosphere show intrinsic properties. Efficiency of solar energy transmittance was enhanced by coating of $SiO_2-ZrO_2$ as an alkali ion barrier layer. Energy was saved by the double layers of $SiO_2-ZrO_2$ and ITO since solar energy is transmitted and heat generated inside(${\lambda}$ > 2700nm) is reflected.

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Phase Transition and Relaxation Properties of Nonlinear-Optical KTP Single Crystal (비선형광학 단결정 KTP의 상전이 및 완화특성에 관한 연구)

  • Choi, Byung-Chun
    • Journal of Sensor Science and Technology
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    • v.7 no.6
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    • pp.386-393
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    • 1998
  • We have carried out the measurements of complex dielectric constants with impedance/gain-phase analyzer using capacitor method and the experiments of high temperature X-ray powder diffraction with X-ray diffractometer using ${\theta}-2{\theta}$ scan method for the KTP single crystal which has the premium nonlinear optical properties. From the results of high temperature X-ray powder diffraction experiments, we have found that KTP does not undergo structural phase transition below $900^{\circ}C$. It is clear that KTP undergoes structural phase transition around $900^{\circ}C$ and belongs to orthorhombic above $900^{\circ}C$ still. However, we have applied phenomenological relation of dielectric relaxation to the results of complex dielectric measurement and have found that relaxation mechanism of KTP well satisfies the Cole-Cole relation over the temperature range from $-78^{\circ}C$ to $200^{\circ}C$. And also the relaxation time well satisfies the Vogel-Fulcher relation. It is regarded that the hopping and thermally activated diffusion mechanism may control the conduction behavior of KTP above $200^{\circ}C$.

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